Rated 5 out of 5 stars

Update: Tip helped, in love with the extension again. --Oh well, mozilla refused my first review (403 error). Short version: current version of autopager eats massive amounts of CPU when switching or closing the tabs (Firefox 5.0.1 portable), making these operations last several seconds.

This review is for a previous version of the add-on (0.6.2.10.1-signed.1-signed). 

There was incorrect rule which caused performance issues. You can try Tools->AutoPager->Update Setting Online to get the lasted rules.